Electric discharge tube



FM 331,, Iififl G. F. ASKER I 2,4953%] ELECTRIC DISCHARGE TUBE FiledApril 4, 1946 m INVENTOR.

GQSTA E ASKER @TTORNEY atented Jan. 31, 1950 w th ELECTRIC DISCHARGETUBE Giista F. Asher, Stockholm, Sweden, assignor to InternationalStandard Electric Corporation,

New York,

N. Y., a corporation of Delaware Application April 4, 1946, Serial No.659,482

Sweden March 22, 1945 Section 1, Public Law 690, August 8, 1946 Patentexpires March 22, 1965 6 Claims. (01. 25027.5)

The present invention relates to electric discharge tubes and moreparticularly to a tube filled with a rare gas or metal vapor. Theinvention more specifically pertains to a tube provided with at leasttwo electrodes and having a low ignition voltage and a low voltage dropof substantially the same value amounting to approximately forty voltsmaximum and prefer ably ranging between five and fifteen volts even whenalternating current is applied across the electrodes.

It is known to provide a gas discharge tube with two cathodes. Suchtubes are the type for the generation of light such as mercury vaporlamps or neon tubes. In such known gaseous discharge devices, thecathodes are so arranged and the gas pressures are so selected that thegreatest voltage drop is obtained in the gas in order to provideeflicient light-producing tubes. These prior tubes having two cathodesrequire about one hundred volts for ignition and the electrodes havebeen of the unheated type.

As distinguished from the prior devices, it is an object of the presentinvention to so arrange the electrodes and to so select the gas pressurethat the voltage drop'in the gas becomes negligible in comparison withthe total voltage drop over the tube.

Another object of the invention is to provide means for preventing thedissipation of heat from the cathodes and to increase the currentcarrying capacity of these electrodes and to provide for there-radiation of heat to the cathodes.

Other objects and features of the invention will be more apparent as thepresent disclosure proceeds and upon consideration of the accompanyingdrawing and the following detailed description wherein an exemplaryembodiment of the invention is disclosed.

In the drawing:

Fig. 1 is an axial sectional view of a tube embodying the invention.

Fig. 2 is a plan view of the tube shown in Fig. 1.

In the embodiment of the invention illustrated in the drawing thegaseous discharge tube is provided with two indirectly heated cathodesmounted on a stem which forms an integral part of the envelope and theseparts of the tube are of the type employed in conventional radio tubes.The cathodes are to increase their current-carrying capacity and at thesame time to re-radiate heat to the cathodes and to prevent dissipationof the heat from these electrodes. The tube may be filled with a raregas or metal vapor such as mercury vapor in provided with screensadapted order that the desired low ignition voltage may be obtained.

Referring to the drawing, the glass envelope is shown at l which may beformed integral with a conventional type stem Bwhich projects upwardlyfrom the base of the tube. The discharge tube includes two indirectlyheated cathodes 2 which are supported by a plurality of heat resistantinsulating plates 3 which may be formed of mica. The filaments forheating the cathodes are shown at 4 and these filaments extend into theinterior of the hollow cathodes 2 in a wellknown manner. The filaments 4are connected in parallel as shown in Fig. 1. The filaments 4 aresupplied with heating current through a pair of leads 9 which extendthrough stem 6 to the base of the tube.

Each cathode is surrounded by a screen 5. The screens 5 may be formed ofmetal and are supported between the mica plates 3. It will be noted thatthe cathodes 2 extend beyond the ends of the screens 5 and projectbeyond the mica plates 3. The screens 5 serve as means for preventingheat radiations from the cathodes and the screens are adapted toincrease the current-carrying capacity of these electrodes. The opposedopen sides of each screen may be provided with shield portions 12adjacent the ends ot the cathodes to protect the glass envelope and stemfrom discharges occurring at the ends of the cathodes. The screens 5 arealso supported by a pair of posts I l which extend upwardly from thestem 6 and may be welded or ptherwise attached to the screen 5. Theposts II also support the mica plates 3.

A pair of leads I extend through the stem of the tube and are connectedto the posts H and therefore provide conductors to the screens 5. Thecathodes are provided with leads 8. The conductors 1 and 8 are connectedto each other either within the tube base or by means of externalconnections as shown in Fig. 1.

If a variable alternating current is impressed across the leads 8 and aresistor is connected in series with an alternating current supply, thenthe peak amplitude of the alternating voltage across the tube will beconstant and approximately of the same magnitude as the ionizationvoltage of the gas even if the current varies within wide limits. If thecathode surface is approximately four square centimeters and the tube isfilled with a rare gas there is provided a substantially constant glowvoltage when the current varies between 10- and 1 ampere With an appliedvoltage of approximately three volts, the current through the tube is ofa magnitude of about 10* amperes. This current decreases rapidly with afall in voltage.

The gas discharge tube herein described may be utilized for manypurposes such as a voltage protector or blocking means in associationwith radio receivers. The tube may, for example, be connected betweenthe antenna of a receiver and ground. Under such circumstances thevoltage cannot reach a value detrimental to the receiver. The voltagesbetween the antenna of a receiver and ground are normally such that thecurrent through the tube becomes so small that the sensitivity of thereceiver is not appreciably influenced. The gaseous discharge tube mayalso be employed for transforming a sine wave alternatlng currentvoltage into alternating current voltage of a reactangular wave shape;Under such circumstances the sine wave alternating current voltage issupplied to the tube in series connection with a resistance. The tubewill then function as a voltage limiting device for the two half wavesof the alternating current voltage so that each will result in asubstantially rectangular wave form.

While the invention has been described with reference to specificstructural details, it will be appreciated that changes may be madetherein such as employing directly heated cathodes. Various othermodifications of the tube structure may be made without departing fromthe spirit and scope of the invention as set forth in the appendedclaims.

I claim:

1. In a gaseous discharge tube, an envelope having a portion of givendiameter, a plurality of electrodes spaced apart at a distance less thansaid diameter, a screen surrounding each electrode on three sides inspaced relation with respect, thereto, and means providing an electricalconnection between each electrode and the associated screen.

2; In a gaseous discharge over-voltage control device of relatively lowvignition potential for signal receiving apparatus, an envelope, twosubstantially parallel cathodes supported from one end of said envelope,a screen embracing one cathode and spaced outwardly therefrom, a screenembracing the other cathode and spaced outwardly therefrom, said screensbeing open toward each other, and an electrical connection between eachcathode and its embracing screen.

3. In a gaseous discharge device for selectively firing at apredetermined low voltage level, an envelope, an ionizable gas fillingsaid envelope, two substantially parallel cathodes mounted in closeadjacency at one end of said envelope, means for heating said cathodes,and a screen substantially enclosing each cathode except the opposingsides thereof.

4. In an electric discharge over-voltage control device of relativelylow ignition potential for signal receiving apparatus, an envelope, astem sealed to said envelope at one end thereof, a pair of postsextending from said stem, a screen having a U-shaped cross-sectionattached to each post, with the open side towards the other post and anelectron emitting electrode mounted within each screen.

5. In an electrical discharge over-voltage control device of relativelylow ignition potential for signal receiving apparatus, an envelopeincluding a stem, a pair of posts extending upwardly from said stem, apair of spaced insulation members supported by said posts, a screenhaving a U- shaped cross-section connected to each post and extendingbetween said insulation members with the open side of said screentowards the other post, and a cathode mounted within each screen.

6. A gas discharge device comprising an envelope, two electron emissivecathodes mounted at one end of said envelope, 2. screen embracing eachcathode but spaced therefrom, each screen being open toward the otherand an ionizable gas within said envelope.

GC'JSTA F. ASKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,815,762 Charlton July 21, 19311,897,482 Kenty Feb. 14, 1933 1,963,008 Weeks June 12, 1934 2,128,051Lowry Aug. 23, 1938 2,157,552 Macksoud May 9, 1939

